This invention relates to fluid filter assemblies including a bypass valve and more particularly to a fluid filter assembly having an improved bypass structure.
Hydraulic circuits and oil lubricating systems generally employ filters to remove contaminants from the fluid. Because of the need for continuous supply of fluid and to prevent rupture of the filter element and the consequent contamination of the fluid, these filter assemblies are provided with a bypass valve. The bypass valve is designed to open when the filter becomes so clogged as to cause a predetermined pressure rise thereacross. The opening of the valve permits fluid to bypass the filter element to supply the demands of the system.
In the prior art, various filter assemblies of such type are known. However, there are three basic considerations involved in designing a fluid filter and bypass assembly some, but not all, of which are met in the filter assemblies of the prior art.
The first consideration is to reduce the likelihood that contaminants trapped by the filter will be carried into the reservoir when the bypass valve is actuated. The second consideration is to avoid aeration of the bypassed fluid resulting not only in the formation of foam in the reservoir, but also in the entrainment of air in the fluid which can be more harmful to the active elements of the hydraulic system than solid contaminants. The third consideration is that the bypass valve structure must be simple and inexpensive to manufacture while providing reliability in operation.
It is a basic object of this invention to provide an improved fluid filter assembly including a bypass valve structure which meets all of the above considerations without complicated design or complex construction.